code: def canonicalize_datetime(dt):
      # Strip out any HHMMSS or timezone info in the user's datetime, so that
      # all the datetimes we return will be 00:00:00 UTC.
      return datetime(dt.year, dt.month, dt.day, tzinfo=pytz.utc)
  
file_path: zipline/zipline/utils/tradingcalendar.py
imports: import pandas
  import pytz
  from datetime import datetime
  from dateutil import rrule
  from functools import partial
label_desc: Use image node_id 1 for calling a global function with example usage: canonicalize_datetime(dt) and returns: datetime